Ratio Enforcer (Letterbox Scale)

RatioEnforcer.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class RatioEnforcer : MonoBehaviour {
    
    [SerializeField] private float targetWidth = 256;
    [SerializeField] private float targetHeight = 240;

    // Use this for initialization
    void Start()
    {
        // set the desired aspect ratio (the values in this example are
        // hard-coded for 16:9, but you could make them into public
        // variables instead so you can set them at design time)
        float targetaspect = targetWidth / targetHeight;

        // determine the game window's current aspect ratio

        float windowaspect = (float)Screen.width / (float)Screen.height;

        // current viewport height should be scaled by this amount

        float scaleheight = windowaspect / targetaspect;

        // obtain camera component so we can modify its viewport

        Camera camera = GetComponent<Camera>();

        // if scaled height is less than current height, add letterbox

        if (scaleheight < 1.0f)
        {
            Rect rect = camera.rect;

            rect.width = 1.0f;

            rect.height = scaleheight;
            rect.x = 0;
            rect.y = (1.0f - scaleheight) / 2.0f;

            camera.rect = rect;

        }
        else // add pillarbox
        {
            float scalewidth = 1.0f / scaleheight;

            Rect rect = camera.rect;

            rect.width = scalewidth;

            rect.height = 1.0f;
            rect.x = (1.0f - scalewidth) / 2.0f;
            rect.y = 0;

            camera.rect = rect;

        }
    }
}